Unless this is going to be your every day all day driver in a very wet environment, "why?" The wiring on most of these girls has lasted a surprising amount of time, in many cases outliving the rusting bodies and still functioning. The bulkhead connector / ammeter circuit is a known problem and voltage drop through the ignition switch can be a problem. Other than that it is take it on one at a time.
Another specific connector in 73 which gave trouble is the white underhood engine harness--to engine bay harness connector. Cut that out, neatly splice the wiring together, and forget about it